What characteristic do many pollen grains of water-pollinated species have to protect them?

Step-by-step solution

Not all aquatic plants use water for pollination. In a majority of aquatic plants such as water hyacinth and water lily, the flowers emerge above the level of water and are pollinated by insects or wind as in most of the land plants. In Vallisneria, the female flower reach the surface of water by the long stalk and the male flowers or pollen grains are released on to the surface of water. They are carried passively by water some of them eventually reach the female flowers and the stigma. In another group of water p